The present invention principally relates to a system for utilizing the various forms of electromagnetic radiation, preferably solar energy, to convert, in a solar reactor, carbon dioxide and carbonaceous matter to carbon monoxide and other gaseous fuel components. Carbon monoxide is a useful source of thermal energy and the present invention therefore permits efficient conversion of solar energy to another form of thermal energy. In a further aspect of the invention carbon monoxide can be converted to a highly purified and useful form of carbon, with the concomitant production of useful heat energy.
The present energy crisis and the demand for environmentally acceptable fossil fuels have made coal conversion imperative and of high priority in proposed national energy programs. In addition, the increasing use of solar energy has dramatized the need for chemical storage of energy forms, such as solar, which are sporadically or intermittently available. No practical chemical radiation energy conversion and storage system exists today, as far as applicant is aware.
It is therefore highly desirable that a system be found that permits the efficient conversion of large reserves of coal or other carbonaceous material to environmentally acceptable energy forms. It is particularly desirable that such a system be capable of utilizing and storing solar energy, in view of the renewable nature of this energy source.
There is prior art patent literature which is relevant to the basic chemical reactions occurring in accordance with the present invention. For example, U. S. Pat. No. 1,812,230 discloses a method of preparing elementary carbon from carbon monoxide at temperatures of 300.degree.-500.degree. C. in the presence of a catalyst. However, normal heat generating means are provided rather than solar energy. Essentially the same disclosure and limitations are disclosed in U.S. Pat. No. 1,865,053, which teaches combining carbon and carbon dioxide to form carbon monoxide, at elevated temperatures, for example, 800.degree.C.-1500.degree. C., and U.S. Pat. No. 2,008,270 similarly discloses the disassociation of carbon monoxide in the presence of a catalyst into useable forms of carbon, and carbon dioxide.
Known prior art also includes reactions of the type described in which various electromagnetic radiations from artificial sources are provided for carrying out the reactions. For example, in U.S. Pat. No. 3,977,952, there is disclosed the irradiation of carbon-containing compounds in gaseous form, such as polluted air or industrial flue gas, for the purpose of decomposition. U.S. Pat. No. 4,045,315 describes the production of hydrogen by the solar photolysis of water, and U.S. Pat. No. 4,070,861 discloses a solar reactor combustion chamber to which are fed molecular hydrogen and chlorine, together with oxygen, to form hydrochloric acid. The reaction is exothermic and the heat and pressure formed can be subsequently utilized as energy sources.
U.S. Pat. No. 3,993,458 relates to a method for producing synthetic fuels from solid waste, and disclosed in this patent is a fluidized bed reactor adapted to be heated by a tower top solar furnace. Although the process is principally concerned with the pyrolysis and gasification of solid organic waste, coal is mentioned as a feed material, and carbon dioxide or steam, or mixtures of these two gases, are used to fluidize the reactive bed which may comprise coal or other waste materials. Although carbon monoxide and carbon dioxide are products of the pyrolysis, the reactions are carried out in a steam atmosphere in the presence of a catalyst. The producer gas obtained from the reaction can be used as the heat source for the working fluid during periods when solar energy is minimized or unavailable. The reactions are carried out at temperatures of 600.degree.C.-700.degree. C., and not in the absence of free oxygen, an important feature of the present invention as will be hereinafter described.
An important aspect of the present invention is the specific design of the solar reactor and the operating conditions maintained therein. Solar heating apparatuses are presently becoming a highly developed area of technology and the following patents are representative of the prior art. U.S. Pat. Nos. 3,655,517 and 3,501,381 disclose solar distillation units in which collecting troughs are provided beneath the glass or window surface to provide means for carrying off the condensate formed on the undersurface of the glass during the distillation process. U.S. Pat. Nos. 3,985,118 and 4,011,857 disclose solar heating systems which utilize lenses for converging and thus concentrating the solar rays toward a focal point for more efficient utilization of the solar energy. The latter patent discloses the positioning of the lens in a housing mounted for controlled movement to permit tracking of the sun for most efficient reception of the solar energy. This feature of tracking is per se well known and also disclosed in U.S. Pat. No. 4,057,401, which discloses a solar heat section in which the glass part of the section is mounted in a sealed housing which moves through a specified angle relative to the horizontal for tracking purposes. It should be noted that in the system, the solar heat is employed to heat air, which is in turn used to heat the digester tanks which form part of the apparatus for manufacturing methane gas.